NEW DELHI -- India's government says it plans to phase out imports of a dirty fuel known as petroleum coke, or "petcoke," after an Associated Press investigation found U.S. oil refineries are exporting vast quantities of the product to India.

But when it comes to domestic use, the Indian government seems to be going in a different direction. The government this week argued in court that restrictions on petcoke around polluted New Delhi should be eased for certain low-impact industries. The move has infuriated environmentalists.

The AP investigation found the U.S. sold about 20 times more petcoke to India last year than it did six years earlier after U.S. refineries struggled to sell the product at home. In 2016, the U.S. sent more than 8 million metric tons of petcoke to India, enough to fill the Empire State Building eight times over.

Petcoke is a bottom-of-the-barrel leftover from the refining of Canadian tar sands crude and other heavy oils. It's cheaper and burns hotter than coal. But laboratory tests on imported petcoke used near New Delhi found it contained 17 times more sulfur than the limit set for coal.

A day after the AP investigation was published, Dharmendra Pradhan, India's minister for petroleum and natural gas, said the government was formulating a policy to end imports.

"We are planning to implement a system to stop imports and use home-produced petcoke for nonpolluting sectors, such as cement production," Pradhan said, according to the Press Trust of India news agency.

He said fuel-hungry India consumes about 25 million metric tons of petcoke each year, nearly half of which is imported.

On Monday, the environment ministry argued in an affidavit against a ban on the use of petcoke and furnace oil in New Delhi and the surrounding states of Uttar Pradesh, Haryana and Rajasthan. The Supreme Court imposed the ban on the three states in October after environmentalist M.C. Mehta filed a petition. The fuels were already banned in the capital.

The ministry said it wanted certain industries such as cement manufacturing to be able to use a small amount of petcoke for about a year until alternatives could be developed.

But Mehta on Wednesday said petcoke has a big impact.

"There is an environmental emergency with New Delhi as one of the most polluted cities in the world. Pollution levels go up by 50 percent if you are burning petcoke," he said. "Is this government a custodian of people's life and health or is it there to benefit some industrialists?"

Mehta said the government typically only takes action on the environment when forced by the Supreme Court, which in India takes an unusually proactive approach to environmental issues.

New Delhi has been choking from air pollution in recent weeks. The air quality typically deteriorates at this time of year because the winds die down, people build street fires to keep warm and farmers burn fields of old crops. The pollution has gotten so bad it has even interrupted India's favorite sport of cricket.

The Supreme Court will hear the government's oral arguments on easing the petcoke ban next week.